1. Technical Field
The present invention relates to optical communications and, in particular, to optical communications using Monte Carlo based log likelihood functions for demodulation.
2. Description of the Related Art
A 100 Gb/s Ethernet standard has been approved and is already being implemented. This implementation is expected to accelerate in next few years. At these ultra-high data rates, the performance of fiber-optic communication systems is degraded significantly due to presence of various linear and nonlinear impairments. To deal with those channel impairments modulation and detection have been proposed to compensate.
For one such compensation technique, carrier phase estimation (CPE), the algorithmic DSP-based approaches are highly popular, and can be categorized into two broad categories: data-aided and non-data-aided. The maximum a posteriori approach is particularly efficient in CPE. However, the complexity of such algorithms grows exponentially with the channel memory. Even upon compensation of chromatic dispersion and nonlinearity phase compensation there will be some residual phase error.